DESCRIPTION This research will be done primarily in Russia as an extension of NIH grant no.GM21457. The research will focus on the interaction of water-soluble polymers with vesicular biomembranes, a topic of considerable biomedical relevance. The project will combine the expertise of the Yaroslavov group in Moscow (photon correlation spectroscopy, laser microelectrophoresis, conductometry etc.) with that of the Menger group (organic synthesis, light and electron microscopy, colloid chemistry). An active collaboration, which has already resulted in several joint publications, has existed for four years, but the time has come when direct support is needed to expand the effort and have the collaboration reach its full potential. The main thrust will be to interact synthetic polymers, with varying content of ionic groups and hydrophobic chains, with giant vesicles that can be observed under the light microscope. Giant vesicles are composed of single phospholipid bilayers and have been shown by the Menger group to undergo "cytomimetic" events including fusion, fission, budding, endocytosis, and aggregation. The effect of polymer structure, and membrane composition, upon these cell-like morphological changes has never been elucidated. Work with giant vesicles will be coupled to work with more conventional large unilamellar vesicles. By using a combination of giant and large vesicles, changes in membrane morphology will be related to molecular structure of interacting polymers as well as composition and properties of polymer-vesicle complexes. The hope, generally speaking, is to obtain a wealth of information on membrane behavior in response to macromolecular binding using defined, structurally controllable systems and both visual and instrumental analyses.